1. Field of the Invention
The present invention relates to a translucent laminate sheet configured to emit white light by means of an organic phosphor and a light-emitting device using the translucent laminate sheet.
2. Description of Related Art
A known example of a conventional light-emitting device comprises an LED (light emitting diode) lamp in which an LED element is mounted on a lead frame or insulative substrate provided with electrodes using an Ag paste and electrically connected to the electrodes by bonding wires, and is thereafter sealed by epoxy resin, silicon resin or the like. In the case of realizing a white-light LED lamp, a blue LED element of a GaN type is mainly used, and the LED lamp is formed by mixing a YAG phosphor in the above-mentioned epoxy resin or the like, so that pseudo white light is emitted by wavelength conversion of light emitted from the blue LED element by the YAG phosphor (for reference, see Japanese Patent Application Publication 2006-49657).
However, because the YAG phosphor is an inorganic phosphor, the wavelength-converted light has a wide spectrum and has poor matching with a liquid crystal color filter, and hence it is difficult to obtain white light having high chromaticness.
In this connection, it is already known in conventional art that addition of a red phosphor to the YAG phosphor in the above-mentioned resin makes it possible to achieve a broader color repeatability. For example, diketone proposed in Japanese Patent Application Publication Nos. 2005-252250 or 2003-81986, or a europium complex, having a ligand of carboxylic acid proposed in Japanese Patent Application Publication 2005-8872 are red emission materials having high emission strength, excellent color rendering properties and excellent color reproducibility.
The complex is sensitive to oxygen or humidity and requires an airtight sealing; in a conventional sealing method, a fluorescent layer is applied to an inner surface of an outer cap in a light-emitting device and an inner portion of the outer cap is set to a vacuum or inert gas ambient atmosphere to achieve the airtight sealing (for reference, see Japanese Patent Application Publication 2004-352928).
However, the above-mentioned proposals do not disclose a light-emitting device which includes a translucent laminate sheet in which an organic phosphor is sealed between two light-transmitting members and in which a position of a light source can be arbitrarily set.